242 EXPERIMENT STATION EECORD. 



DISEASES OF PLANTS. 



The constancy of mutants; the origin of disease resistance in plants, 

 H. L. BoLLEY (Amer. Breeders' Assoc. [Proc], 4 (1908), pp. 121-129).— A criti- 

 cism and discussion of De Vries's mutation theory is given, and attention is 

 called by the author to what he believes to be a fundamental principle of plant 

 breeding, namely, that in order to maintain a standard of a crop the condition 

 under which a character is originated or is being originated must be maintained 

 or at least approximated. 



A description is given of the author's work iu developing disease resistance 

 in plants and of the results obtained, and from his Observations he is led to 

 conclude "(1) that mutations may be so insignificant and numerous as to be 

 unrecognizable and thus fall directly into the class called by De Vries ' fluctuat- 

 ing variations,' or (2) that they may be induced in a mixture of a great number 

 of varieties of a species at one and the same time because of the same environ- 

 mental causes, or (3) that in some cases 'fluctuating variations' are of such 

 nature and worth as to allow results to be obtained in mass breeding of as great 

 importance as any that we may hope to obtain by looking for a single mutating 

 type." 



In relation to disease resistance, the author states that he is unable to deter- 

 mine whether resistance is due to structural or physiological changes in the 

 plant. There appears to be some evidence pointing to the probable influence of 

 chemical agencies, such as toxins, arising from the direct existence of fungus 

 attacks upon the hosts. 



Comparative investigations on the effect of various methods of seed 

 treatment on the germination of seed, H. Burmester [Ztsehr. Pflanzenkrank., 

 18 (1908), No. 3, pp. 15'f-187). — Laboratory and field studies were made to 

 determine the effect of various seed treatments recommended for the prevention 

 of cereal smuts. Among the fungicides tested on oats, wheat, and barley were 

 copper sulphate, Bordeaux mixture, sulphuric acid, Ceres powder, formalin, 

 hot water, hot air, and picric acid, the effect on the seed being determined by 

 germination tests. 



Soaking the grain for 14 hours in copper sulphate solutions ranging from 

 0.5 to 2 per cent proved injurious to all seeds whether limed or not, although 

 the oats were much less injured than the other grains. Treating the seed with 

 2 per cent Bordeaux mixture which was allowed to dry on the grain was not 

 injurious. Sulphuric acid proved unsutiable for the treatment of grain for 

 smut prevention. Ceres powder proved somewhat injurious to all the grains. 

 Strong solutions of formalin reduced germination, but when seed was soaked 

 for 4 hours in 0.1 per cent solutions or less all the grains gave high germina- 

 tions. Soaking the seed for 5 minutes in water heated to about 5.3° C. was only 

 slightly injurious to wheat but somewhat destructive of oats and barley. 

 Treating seed grain with air heated to 75° C. slightly reduced its germinative 

 power, but the treated grains sprouted more quickly than the untreated, and 

 this method seems worthy of extended use. Picric acid, and especially the form 

 called Reflorit, is useless as a disinfection material. 



In field practice treating tlie seed grain with copper sulphate with or without 

 liming and the use of formalin are recommended as the most eflicient means 

 of controlling smut. 



Notes on some potato diseases, W. Kreitz (IUus. Landiv. Ztff., 29 {1909), 

 No. 18, p. 176, figs. 5). — Descriptions are given of a number of forms of potato 

 scab, among them the pock scab, the conunon scab, and the black scab or 

 canker caused by Chrysophlyctis endobioUca. 



